Conventionally, data written onto a magnetic disk sometimes includes a continuous pattern of 0 or 1, or a repetitive pattern such as 0101 . . . . In this case, it may be difficult to achieve synchronization at read or difficult to recover original write data due to deterioration of signal quality.
Accordingly, in recent years, a technique has been proposed in which for writing data onto the magnetic disk, a run length of a continuous pattern and a number of repetitive patterns (number of times of magnetization reversal) are limited by using modulation codes such as RLL codes and MTR codes.
Encoding with the modulation codes, however, may increase redundancy and deteriorate format efficiency.